Re: [Linux-fbdev-devel] [RFC] fbdev & power management

[James S. <jsi...@li...>]

>Ewww, that means that all possible video modes must be listed in a table
>in the kernel?

No. Of course we kind of do that now with modedb. It is the same as now.
The only difference is it goes threw the tty layer to the fbcon layer
instead of from userland to fbdev layer to tty layer. It makes for a
consistant interface for mode changing for all console drivers. It also
allows for a resize_vc function which in turn allows for a generic VC
switching function. No more con_switch is needed. The next benfiet is
since it is coming from the tty layer we have modes of columns*font width
by rows*font height. We don't need code to deal with case if the number of
columns is 80 and 1/2. Now if we are stuck with a system where the card
mode is set and can't be changed we then do the opposite and look for a
font set that makes the mode perfect. If we can't find one well its time
to provide a special font for that system.

>I'd prefer to keep the current situation because it is has the "policy"
>in user space, ie, the video programming information.

Hah? Policy is still in userspace. You just express the resolution in
columns and rows instead of pixels. You could express it in pixels as well
since struct winsize allows this. I haven't implemented it yet since it
also requires dealing with possible font handling. Yuck!

>That seems like a great step backwards to me.  For instance, how do you
>handle the case where you want to support:
>
>        FBCon Text, 80x30 @ 50Hz
>        FBCon Text, 80x30 @ 60Hz

With FB_ACTIVATE_NXTOPEN. The question you have to ask yourself is why do
you need this specifically if you are going to be using fbdev only as a
text console ? [below]

>We already fully support this on ARM machines since one of theapplications
>of ARM boxen are web-top devices, which are required to produce TV
>compatible signals.

Are you still using fbdev just as a text console here or are we talking
here a app that opens /dev/fb and uses /dev/fb. If that is the case then
the card is the only limit. If not and for some reason you need the
graphical console while needing to produce TV compatiable signals then you
can

a) Make the default fb_var_screeninfo compatible to produce TV signals in
   the driver.

b) Use modedb to select the mode you want.

c) Open /dev/fb but use the FB_ACTIVATE_NXTOPEN flag to preserve the
   hardware state to what you want when going back to fbcon.

MS: (n) 1. A debilitating and surprisingly widespread affliction that
renders the sufferer barely able to perform the simplest task. 2. A disease.

James Simmons  [jsi...@li...]               ____/|
fbdev/console/gfx developer                             \ o.O|
http://www.linux-fbdev.org                               =(_)=
http://linuxgfx.sourceforge.net                            U
http://linuxconsole.sourceforge.net